The challenge in this puzzle is to place the values 1 to 9 in each triangle in Step 3 so that the sum of each big triangle (the 3 triangles with 2 matches on each side) is equal to 25.
Lets start from the beginning! Take 8 matchsticks and break each stick into 5 pieces as illustrated in Step 1. Step 2 shows how the numbers 1 to 9 are represented by the broken sticks. Now put the broken sticks in the triangles in Step 3 so that the total of each big triangle is equal to 25.
Note that the number 10 has already been placed for you and that this is the common number in each of the 3 big triangles.